User's Manual

Table Of Contents
R01UH0823EJ0110 Rev.1.10 Page 194 of 1852
Nov 30, 2020
RX23W Group 9. Clock Generation Circuit
9.2.15 Oscillation Stop Detection Status Register (OSTDSR)
Note: Set the PRCR.PRC0 bit to 1 (write enabled) before rewriting this register.
Note 1. This bit can only be set to 0.
OSTDF Flag (Oscillation Stop Detection Flag)
This bit is a flag to indicate the main clock status. When the OSTDF flag is 1, it indicates that the main clock oscillation
stop has been detected.
Once the main clock oscillation stop is detected, the OSTDF flag is not set to 0 even though the main clock oscillation is
restarted. The OSTDF flag is set to 0 by reading 1 from the bit and then writing 0. At least three ICLK cycles of wait time
is necessary between writing 0 to the OSTDF flag and reading the OSTDF flag as 0. If the OSTDF flag is set to 0 while
the main clock oscillation is stopped, the OSTDF flag becomes 0 and then returns to 1.
When the main clock oscillator (010b) or PLL (100b) is selected by the clock source select bits in system clock control
register 3 (SCKCR3.CKSEL[2:0]), the OSTDF flag cannot be modified to 0. The OSTDF flag should be set to 0 after
switching the clock source to a source other than the main clock oscillator and the PLL.
[Setting condition]
The main clock oscillation is stopped with the OSTDCR.OSTDE bit being 1 (oscillation stop detection function
enabled).
[Clearing condition]
1 is read and then 0 is written when the SCKCR3.CKSEL[2:0] bits are neither 010b nor 100b.
Address(es): 0008 0041h
b7 b6 b5 b4 b3 b2 b1 b0
———————OSTDF
Value after reset:
00000000
Bit Symbol Bit Name Description R/W
b0 OSTDF Oscillation Stop Detection Flag 0: The main clock oscillation stop has not been detected.
1: The main clock oscillation stop has been detected.
R/(W)
*
1
b7 to b1 Reserved These bits are read as 0 and cannot be modified. R